WORKPLACE SAFETY AND INSURANCE APPEALS TRIBUNAL DECISION NO. 1100/13

Transcription

1 WORKPLACE SAFETY AND INSURANCE APPEALS TRIBUNAL DECISION NO. 1100/13 BEFORE: M. Crystal: Vice-Chair HEARING: June 10, 2013 at Toronto Written DATE OF DECISION: August 30, 2013 NEUTRAL CITATION: 2013 ONWSIAT 1875 DECISION UNDER APPEAL: WSIB ARO decision dated November 30, 2010 APPEARANCES: For the worker: For the employer: Interpreter: Ms. H. Ethier, Office of the Worker Adviser Did not participate Not applicable Workplace Safety and Insurance Appeals Tribunal Tribunal d appel de la sécurité professionnelle et de l assurance contre les accidents du travail 505 University Avenue 7 th Floor 505, avenue University, 7 e étage Toronto ON M5G 2P2 Toronto ON M5G 2P2

2 Decision No. 1100/13 REASONS (i) Introduction [1] This appeal was considered as a written case in Toronto, on June 10, The worker appeals the decision of Appeals Resolution Officer (ARO) D. McParland, dated November 30, That decision determined that: i) The worker is not entitled to benefits for myeloid leukemia resulting from his workplace exposures while he was employed as a miner; and ii) The worker s estate is not entitled to survivor benefits. [2] The worker was represented by Ms. H. Ethier, Office of the Worker Adviser. The employer did not participate in the appeal. Ms. Ethier provided written submissions, dated December 12, (ii) The issue under appeal [3] The issues to be determined in this appeal are i) Whether the worker has initial entitlement to benefits for myeloid leukemia resulting from his workplace exposures while he was employed as a miner; and ii) Whether the worker s estate is entitled to survivor benefits. (iii) The evidence [4] The factual basis of this appeal does not appear to be contentious. As noted in both the ARO decision and the submissions provided by the worker s representative, the worker was employed at the employer s uranium mine from 1968 to He developed flu like symptoms in 2004 and was initially diagnosed with myelodysplastic syndrome. A bone marrow biopsy was done in May 2005 which confirmed a diagnosis of acute myeloid leukemia. The worker underwent treatment but passed away on April 21, 2006, due to his illness. [5] The worker established an accident claim by sending correspondence, dated November 10, 2005, to the Board s Occupational Disease and Survivors Benefits Program. The correspondence stated in part: I would like to establish a claim for my leukemia I attribute to my employment as follows: [The accident employer] February 1968 to March 1992 I was employed as a miner, up until 1969, and then I went on the service crew and eventually as a rock breaker operator. I was exposed to silica dust, radiation, and diesel exhaust primarily at the dump point where the heavy equipment would dump ore for me to break with the rock breaker. In addition I worker [sic] occasionally on the conveyor belts in poor ventilation. I was diagnosed in May 2005 by Dr. Gill my specialist [6] At the request of the Board s Manager, Occupational Disease and Survivor Benefits Program (ODSBP), a research memo, dated March 29, 2007, entitled Risk of Leukemia in

3 Page: 2 Decision No. 1100/13 Uranium Miners was prepared by Reimar Gaertner, Manager of the Board s Occupational Disease Policy and Research Branch. The memo began by providing a description of the nature of radiation. In this regard, the memo stated: You had received some conflicting information about the risk of leukemia after exposure to the types of radiation experienced in underground uranium mining. You asked me to clarify current understanding of this risk in relation to Ontario uranium minors. First, a few brief words about what radiation is. Radiation is energy that comes from a source and travels through a material or through space. Light and heat are common examples. We are particularly interested in ionizing radiation that has enough energy to produce charged particles (ions) when contacting matter. This type of radiation can cause changes in cells leading to cancer. Ionizing radiation is produced by unstable atoms that are referred to as radioactive. There are primarily three types of ionizing radiation, all of which can be produced during the decay processes of radioactive elements: High energy electromagnetic radiation, such as x-rays and gamma radiation. This radiation travels many meters in air and many centimeters in human tissue. Beta radiation is a particulate radiation that consists of high energy electrons. It can penetrate a few millimeters of human tissue, but this type of radiation has little impact on miners and is not specifically discussed below. Alpha radiation is also a particulate radiation that consists of high energy helium nuclei. This relatively heavy particle has no ability to penetrate even the outer dead layers of skin. But it can be harmful if the unstable atoms that release alpha radiation are ingested or inhaled. There is a great deal of scientific information on the cancer hazards associated with various types and levels of radiation exposure. A clear causal association has been identified between ionizing gamma radiation and leukemia in humans based on high-dose medical exposures and on atomic bomb survivors. The scientific overview below focuses on the types of radiation exposures in uranium miners, and the risk of leukemia in this occupational group. Ionizing radiation Primarily two types of ionizing radiation are discussed below: external gamma rays; and internal alpha-emitters from radon-decay products. The gamma radiation in uranium mines comes from the surrounding rock, and can pass right through the body. This is therefore referred to as external radiation. The dose from this radiation is usually measured in units of milli-sieverts (msv). Radon gas released from the rock produces particulate radioactive breakdown products that are dispersed in the air, and can be inhaled into the lungs. The radioactive alpha particles released from these products essentially only irradiate the tissue in contact with the particles. These are therefore referred to as internally deposited radionuclides. This internal radiation exposure, due primarily to inhalation of rapidly decaying radon progeny, is usually measured In Working Level Months (WLM). This unit would take into account the similar radioactive decay products from thoron, another gas that also may be present in a mine. A third form of radiation in mines is the long-lived radionuclides that come from radioactive decay of uranium in the ore. These slowly-decaying radioactive elements in mine dust contribute little to the overall radiation burden in miners compared to the short lived radon progeny. The levels of gamma radiation in a mine are relatively low and constant, while radon and radon progeny levels, thoron and thoron progeny, as well as uranium dust, are greatly affected by ventilation. Therefore the internal versus external types of radiation may not

4 Page: 3 Decision No. 1100/13 be well correlated with each other in uranium mines, and a measure like WLM may tell us little about gamma radiation exposures. But generally speaking, the short-lived radon progeny decay products represent the major cancer hazard for uranium miners. This cancer hazard is based on clear evidence that elevated lung cancer risk is related to the dose of radon progeny to the lung. The evidence for leukemia risk is reviewed below. [7] The memo then provided a review of some scientific/medical literature relating to the issue of the extent of risk for leukemia associated with exposures from uranium mining. The memo provided the following summary of the literature: Summary There is positive evidence that elevated lung cancer risk is related to the dose of radon progeny to the lung. There is positive evidence that high external gamma radiation exposure increases the risk of leukemia. Results suggest the relative risk of leukemia is elevated approximately two-fold or more after a radiation dose of more than 500 msv to the red bone marrow. This finding applies to leukemia overall and the AML subtype. The risk of developing other leukemia subtypes appears to require higher doses, with CML, ALL, and CLL requiring progressively higher doses. There is inconclusive evidence that gamma radiation exposure below 400 msv significantly increases the risk of leukemia. There is evidence suggesting no association between radon and radon progeny exposure and risk of leukemia. Despite the potential for high exposures in miners, the potential dose to red bone marrow is orders of magnitude lower than that to the lung. The preponderance of findings in large cohort studies with good exposure information indicate no elevated leukemia risk, even after very high exposures. [8] The case materials included a report, dated March 11, 2009, prepared by Dr. P. Jugnundan, a physician with the Occupational Health Clinics for Ontario Workers Inc. (OHCOW). His report stated: The medical information on file has been reviewed. It is noted that [the worker] had a 24 year history of exposure in his workplace. His main exposures consisted of diesel exhaust fumes, silica, ionizing radiation, coal dust (including uranium and radon). The specifics of each exposure have been discussed in detail by the Industrial Hygienist, Mr. Masood Ahmed and I am in agreement with that. Therefore, given his long term exposure, poor work place practices and the almost nonexistent use of personal protective equipment, his exposure to chronic low dose radiation in the form of uranium and radon and his exposures to PAH s [polyaromatic hydrocarbons] from the diesel fume exposure, it is possible that his exposure resulted in his leukemia. It is also noted that no other risk factors were identified that would have resulted in this disease. Therefore, in the absence of any risk factors and the only risk factor being his occupational exposure, it is more likely that his occupational exposure resulted in his leukemia. [9] As noted in Dr. Jugnundan s report, a document entitled Occupational Hygiene Assessment was prepared by M. Ahmed, occupational hygienist with OHCOW. This document was included in the case materials. The document indicated that the worker had been diagnosed with Chronic Myelogenous Leukemia (CML) and that this was the cause of his death. It noted

5 Page: 4 Decision No. 1100/13 that the worker had been a miner for four years and a rock breaker for 20 years, and that as a rock breaker the worker worked in poorly ventilated areas and that he did not use personal protective equipment (PPE). [10] The document stated that the worker was exposed to coal dust during his two years employed in a coal mine, however, other information included in the case materials indicated that this employment occurred in Europe, prior to the worker s arrival in Canada. The document provided discussion of the effects of exposure to coal dust, ionizing radiation, silica and diesel exhaust. The document did not indicate a linkage between coal dust or silica exposure and leukemia. [11] The document stated that increased risk of developing leukemia was also found among underground uranium miners from radon and its progeny exposure based on a study to investigate the relationship between radon exposure and incidence of leukemia, lymphoma or multiple myeloma in Czech uranium miners. The study was published in 2006, and the document included a citation for the study. The document stated that the RR [relative risk] for Myeloid leukemia and non-hodgkin s lymphoma was not statistically significant but they are associated with radon exposure. [12] The document also linked exposure to diesel exhaust to risk of cancer generally, noting that diesel exhaust contains some PAHs, and that a linkage has been demonstrated as between exposure to PAHs and leukemia. [13] The document concluded by stating: Keeping in view the literature review and work history of [the worker] it can be said that he was exposed to radon and diesel exhaust and both these contaminants have potential for causing leukemia. However, the risk of developing myeloid leukemia from radon exposure is low. Moreover, PAHs constitutes a very small portion of diesel exhaust. So, it can be said that the radon and PAHs exposures were low and did not cause significant threat for myeloid leukemia, if each exposure is considered a separate exposure. A more practical approach in occupational exposure assessment would compel us to consider occupational exposure as a mixture of different chemicals or contaminants. In this case radon exposure combined with PAHs in the mixture might have a synergistic effect, in causing leukemia. Synergistic effect of radon and PAHs combined with poor ventilation at work site, latency period of 24 years, and inadequate or no use of PPE could possibly have caused myelogenous leukemia in this case. [14] The case materials also included a review of the worker s radiation dose exposure, that was prepared by Dr. H. Kabir, the Board s Occupational Hygienist. Dr. Kabir s memo on this subject, dated January 28, 2010, stated: ISSUE: Request for a review of radiation dose and benzene exposure of this uranium miner who died from acute myeloid leukemia. REVIEW & COMMENTS: 1. First of all, the whole body external beta-gamma radiation dose as it is obtained from Health Canada is 30.8 msv (milli-sievert), which is well below the exposure limit regulated by the Atomic Energy Control Board of Canada (AECB). 2. Secondly, the total radon progeny dose in WLM is WLM. This dose is to the lung and is assessed under the WSIB policy for uranium miners lung cancer claim only. There is no policy for leukemia and radon progeny dose in WLM.

6 Page: 5 Decision No. 1100/13 3. Thirdly, there is no benzene exposure or known leukomogenic agents exposure known to us for uranium miners underground. In file there is a document quoted as Exposure Assessment (another miner)[ ] also for the leukemia, documents the contents of diesel and diesel fumes and the chemical agents for which monitoring data are available. Please note that no significant benzene exposure is recorded in diesel exhausts world-wide. This claimant did not work in a coal mine in Canada and the exposures the OHCOW is referring to is not relevant. [15] The case materials also included a document entitled Exposure Assessment Review and Comments that was prepared by Dr. Kabir in 2006, in relation to an accident claim for a different worker, who was employed between 1979 and 1992 by the same employer as the worker in this appeal. The worker s name and other identifying information was redacted from the document, so as to anonymize the document vis-a-vis the other worker. The other worker was also making a claim for leukemia, and analysis was provided in relation to the worker s likely level of exposure to diesel and diesel fumes, and the effect of such exposure. The document referred to an IARC (International Agency for Research on Cancer) Monograph related to risk from diesel exhaust, based on contaminants monitored in various bus garages all over the world. The document stated that the results clearly indicate that the level of benzene in diesel exhaust is negligible and the respirable dust with PAHs level is not high. (iv) Applicable law [16] The worker was diagnosed with acute myeloid leukemia in 2005, having first developed symptoms in Accordingly, the worker s entitlement to benefits in this appeal is governed by the Workplace Safety and Insurance Act, (v) Analysis [17] Having reviewed the evidence on file, I find that it is not probable that the worker s acute myeloid leukemia is related to his work exposures as a uranium miner. [18] As a starting point for the analysis, I note that there is no medical information prepared by any of the worker s treating physicians while the worker was alive, which indicated or suggested the possibility that the worker s leukemia might be occupationally related. [19] I note that the worker s letter to the Board, dated November 10, 2005, indicated that he was advancing his claim to the Board on the basis of exposure to silica dust, radiation and diesel exhaust. The report, dated March 11, 2009, prepared by Dr. Jugnundan advances similar occupational exposures of diesel exhaust fumes, silica, ionizing radiation, coal dust (including uranium and radon). [20] I note that the worker did not work in a coal mine in Ontario, and that accordingly the worker s exposure to coal dust cannot be taken directly into account in this appeal. It could possibly be taken into account as part of the synergistic effect, advanced in Mr. Ahmed s document, in that it might have combined with other occupational exposures to affect the worker, but because there was no exposure to coal dust in Ontario, it need not be addressed as an individual or separate exposure that could be related to the worker s leukemia. To that extent, my discussion, set out below, in relation to the probability that the worker s leukemia should be related to the synergistic effect of the occupational exposures combined, is applicable.

7 Page: 6 Decision No. 1100/13 [21] I also note that there was no persuasive information before me indicating that exposure to silica dust can be related to leukemia. Accordingly, exposure to silica dust will not be addressed further in these reasons. [22] The remaining exposures advanced in this case are in relation to ionizing radiation associated with uranium and radon, and exposure to diesel fumes. [23] The evidence indicated that the worker s exposure to ionizing radiation was too low for it to be considered a significant risk factor for leukemia. I note that the memo prepared by Reimar Gaertner, stated that there was positive evidence that high external gamma radiation exposure increases the risk of leukemia and that results suggest the relative risk of leukemia is elevated approximately two-fold or more after a radiation dose of more than 500 msv to the red bone marrow. Dr. Kabir indicated in his memo, dated January 28, 2010, however, that in the worker s case, the whole body external beta-gamma radiation dose as it is obtained from Health Canada is 30.8 msv and that this is well below the exposure limit regulated by the Atomic Energy Control Board of Canada. [24] Mr. Gaertner s paper also indicated that there is evidence suggesting no association between radon and radon progeny and risk of leukemia. [25] This information provided by Mr. Gaertner is also consistent with the information provided by Mr. Ahmed, the occupational hygienist with OHCOW, who acknowledged in his document that the risk of developing myeloid leukemia from radon exposure is low. Accordingly, on the basis of the information provided by Mr. Gaertner and Mr. Ahmed, I conclude that it is not probable that the worker s exposure to radiation contributed significantly to his leukemia. The medical/scientific information indicated external gamma radiation and radiation from radon as the potential radiation exposures that could be related to leukemia, and I am satisfied that the worker s exposure in that regard was not sufficient for it to be considered significant. I also accept Mr. Gaertner s view that the scientific information supports the conclusion that exposure to radon is not a risk factor for leukemia. [26] The remaining factor to consider is the worker s exposure to diesel fumes. Mr. Ahmed indicated in his document that diesel fumes may contain PAHs, and exposure to PAHs has been linked to leukemia. The information before me did not provide another basis for exposure to diesel fumes to be considered as a factor contributing to leukemia. I note, that the Exposure Assessment prepared for another worker, at the same site and over much of the same time period as the worker in this appeal, indicated that according to an IARC Monograph, the respirable dust with PAHs level is not high in relation to diesel. This is also consistent with the information provided in Mr. Ahmed s document, which stated that PAHs constitutes a very small portion of diesel exhaust and that it can be said that the radon and PAHs exposures were low and did not cause significant threat for myeloid leukemia, if each is considered a separate exposure. [27] On this basis, I conclude that, at least when considered separately, it is not probable that the worker s occupational exposures contributed significantly to the development of his leukemia. The fact that the worker s exposure to radiation and diesel fumes, at least considered separately, cannot be significantly related to his leukemia is supported by the information provided by Mr. Gaertner and Mr. Ahmed, and the levels of exposure indicated in Dr. Kabir s memo, dated January 29, There was no evidence before me which implicated exposure to

8 Page: 7 Decision No. 1100/13 silica dust as a factor related to leukemia. The worker was not exposed to coal dust in Ontario. These were the exposures considered in this appeal. [28] Mr. Ahmed has advanced the theory however, that although the worker s individual exposures cannot be implicated as contributing significantly to his leukemia when considered individually, when considered together, it is probable that they contributed significantly to the worker s leukemia as a result of the synergistic effect of the exposures. From the evidence that is before me, however, I am not able to reach the conclusion that the worker s leukemia can be related to such a synergistic effect of the worker s occupational exposures. The case materials did not include any studies or other scientific or medical information to support such a conclusion. The only information in support of this proposition is the statement itself, made by Mr. Ahmed, that this synergistic effect could possibly have caused myelogenous leukemia in this case. [29] I also note that the standard of proof in this appeal, is the evidentiary standard of on a balance of probabilities. Evidence that it is possible that the synergistic effect of the worker s occupational exposures may be related to his leukemia, does not satisfy this standard of proof. I also note that Dr. Jugnundan indicated in his brief report that it is possible that his exposure resulted in his leukemia [emphasis added]. [30] I note that, at the end of his report, Dr. Jugnundan indicated that no other risk factors were identified that would have resulted in this disease and that in the absence of any risk factors and the only risk factor being his occupational exposure, it is more likely that his occupational exposure resulted in his leukemia. I am not able to find that it is probable that the worker s occupational exposures were related to his leukemia, on this basis. In many cases, the probable causes of cancer remain unknown. It does not follow that where one or more risk factors for a particular condition are identified, that because other risk factors have not been identified, the identified risk factor or factors must be implicated as a significant contributor to the condition. This is particularly true in a case where it is acknowledged that the risk associated with the identified factors is low. This approach does not take into account the fact that the current state of scientific knowledge may not be sufficient to determine the ultimate cause of the condition. This approach also does not consider the likelihood that the condition is related to non-occupational factors that cannot be identified. [31] For these reasons, I am not able to conclude on the basis of the evidence before me that the worker s occupational exposures as a uranium miner contributed significantly to the development of acute myelogenous leukemia. Accordingly, the appeal is denied.

9 Page: 8 Decision No. 1100/13 DISPOSITION [32] The appeal is denied. 1. The worker s estate is not entitled to benefits for the worker s acute myelogenous leukemia. 2. The estate is not entitled to survivor benefits. DATED: August 30, 2013 SIGNED: M. Crystal